The Proximal Tubule as the Pathogenic and Therapeutic Target in Acute Kidney Injury

BACKGROUND

In 2004, the term acute kidney injury (AKI) was introduced with the intention of broadening our understanding of rapid declines in renal function and to replace the historical terms of acute renal failure and acute tubular necrosis (ATN). Despite this evolution in terminology, the mechanisms of AKI have stayed largely elusive with the pathophysiological concepts of ATN remaining the mainstay in our understanding of AKI.

SUMMARY

The proximal tubule (PT), having the highest mitochondrial content in the kidney and relying heavily on oxidative phosphorylation to generate ATP, is vulnerable to ischaemic insults and mitochondrial dysfunction. Histologically, pathological changes in the PT are more consistent than changes to the glomeruli or the loop of Henle in AKI. Physiologically, activation of tubuloglomerular feedback due to PT dysfunction leads to an increase in preglomerular afferent arteriole resistance and a reduction in glomerular filtration. Pharmacologically, frusemide - a drug commonly used in the setting of oliguric AKI - is actively secreted by the PT and its diuretic effect is compromised by its failure to be secreted into the urine and thus be delivered to its site of action at the loop of Henle in AKI. Increases in the urinary, but not plasma biomarkers, of PT injury within 1 h of shock suggest that the PT as the initiation pathogenic target of AKI.

KEY MESSAGE

Therapeutic agents targeting specifically the PT epithelial cells, in particular its mitochondria - including amino acid ergothioneine and superoxide scavenger MitoTEMPO - show great promises in ameliorating AKI.

Incidence and Determinants of Mental Health Service Use After Bariatric Surgery

Importance

Obesity is associated with an increased prevalence of psychiatric disorders. The association of bariatric surgery with mental health outcomes is poorly understood.

Objective

To investigate the association of bariatric surgery with the incidence of outpatient, emergency department (ED), and inpatient mental health service use.

Design, Setting, and Participants

This statewide, mirror-image, longitudinal cohort study used data from Western Australian Department of Health Data Linkage Branch records from all patients undergoing index (ie, first) bariatric surgery in Western Australia over a 10-year period (January 2007-December 2016), with mean (SD) follow-up periods of 10.2 (2.9) years before and 5.2 (2.9) years after index bariatric surgery. The data analysis was performed between November 2018 and March 2019.

Exposures

Index bariatric surgery.

Main Outcomes and Measures

The incidence and predictors for mental health presentations, deliberate self-harm, and suicide in association with the timing of bariatric surgery.

Results

A total of 24 766 patients underwent index bariatric surgery; of these, the mean (SD) age was 42.5 (11.7) years and 19 144 (77.3%) were women. Use of at least 1 mental health service occurred in 3976 patients (16.1%), with 1401 patients (35.2%) presenting only before surgery, 1025 (25.8%) presenting before and after surgery, and 1550 patients (39.0%) presenting only after surgery. There was an increase in psychiatric illness presentations after bariatric surgery (outpatient clinic attendance: incidence rate ratio [IRR], 2.3; 95% CI, 2.3-2.4; ED attendance: IRR, 3.0; 95% CI, 2.8-3.2; psychiatric hospitalization: IRR, 3.0; 95% CI, 2.8-3.1). There was also a 5-fold increase in deliberate self-harm presentations to an ED after surgery (IRR, 4.7; 95% CI, 3.8-5.7), with 25 of 261 postoperatives deaths (9.6%) due to suicide. Complications after bariatric surgery requiring further surgical intervention and a history of mental health service provision before surgery were the most important associations with subsequent mental health presentations after surgery. Deliberate self-harm and mental and behavioral disorders due to psychoactive substance use before bariatric surgery were the main associations with subsequent deliberate self-harm or suicide after surgery.

Conclusions and Relevance

We observed an increase in mental health service presentations after bariatric surgery, particularly among those who had prior psychiatric illnesses or developed surgical complications requiring further surgery. These findings caution the hypothesis that weight reduction by bariatric surgery will improve mental health in patients with obesity.

Advance care planning documentation strategies; goals-of-care as an alternative to not-for-resuscitation in medical and oncology patients. A pre-post controlled study on quantifiable outcomes

BACKGROUND

Health services in Tasmania, Victoria and now Western Australia are changing to goals-of-care (GOC) advance care planning (ACP) documentation strategies.

AIM

To compare the clinical impact of two different health department-sanctioned ACP documentation strategies.

METHODS

A non-blinded, pre-post, controlled study over two corresponding 6-month periods in 2016 and 2017 comparing the current discretional not-for-resuscitation (NFR) with a new, inclusive GOC strategy in two medical/oncology wards at a large private hospital. Main outcomes were the uptake of ACP forms per hospitalisation and the timing between hospital admission, ACP form completion and in-patient death. Secondary outcomes included utilisation of the rapid response team (RRT), palliative and critical care services.

RESULTS

In total, 650 NFR and 653 GOC patients underwent 1885 admissions (mean Charlson Comorbidity Index = 3.7). GOC patients had a higher uptake of ACP documentation (346 vs 150 ACP forms per 1000 admissions, P < 0.0001) and a higher proportion of ACP forms completed within the first 48 h of admission (58 vs 39%, P = 0.0002) but a higher incidence of altering the initial ACP level of care (P = 0.003). All other measures, including ACP documentation within 48 h of death (P = 0.50), activation of RRT (P = 0.73) and admission to critical (P = 0.62) or palliative (P = 0.81) care services, remained similar. GOC documentation was often incomplete, with most sub-sections left blank between 74 and 87% of occasions.

CONCLUSION

Despite an increased uptake of the GOC form, overall use remained low, written completion was poor, and most quantitative outcomes remained statistically unchanged. Further research is required before a wider GOC implementation can be supported in Australia's healthcare systems.

Out-of-office hours' elective surgical intensive care admissions and their associated complications

BACKGROUND

The 'weekend' effect is a controversial theory that links reduced staffing levels, staffing seniority and supportive services at hospitals during 'out-of-office hours' time periods with worsening patient outcomes. It is uncertain whether admitting elective surgery patients to intensive care units (ICU) during 'out-of-office hours' time periods mitigates this affect through higher staffing ratios and seniority.

METHODS

Over a 3-year period in Western Australia's largest private hospital, this retrospective nested-cohort study compared all elective surgical patients admitted to the ICU based on whether their admission occurred 'in-office hours' (Monday-Friday 08.00-18.00 hours) or 'out-of-office hours' (all other times). The main outcomes were surgical complications using the Dindo-Clavien classification and length-of-stay data.

RESULTS

Of the total 4363 ICU admissions, 3584 ICU admissions were planned following elective surgery resulting in 2515 (70.2%) in-office hours and 1069 (29.8%) out-of-office hours elective ICU surgical admissions. Out-of-office hours ICU admissions following elective surgery were associated with an increased risk of infection (P = 0.029), blood transfusion (P = 0.020), total parental nutrition (P < 0.001) and unplanned re-operations (P = 0.027). Out-of-office hours ICU admissions were also associated with an increased hospital length-of-stay, with (1.74 days longer, P < 0.0001) and without (2.8 days longer, P < 0.001) adjusting for severity of acute and chronic illnesses and inter-hospital transfers (12.3 versus 9.8%, P = 0.024). Hospital mortality (1.2 versus 0.7%, P = 0.111) was low and similar between both groups.

CONCLUSION

Out-of-office hours ICU admissions following elective surgery is common and associated with serious post-operative complications culminating in significantly longer hospital length-of-stays and greater transfers with important patient and health economic implications.

A Comparison of Bariatric Surgery in Hospitals With and Without ICU: a Linked Data Cohort Study

BACKGROUND

It is uncertain whether bariatric surgery can be safely performed in secondary hospitals without on-site intensive care unit (ICU) support. This study describes the outcomes of elective bariatric surgery patients who required inter-hospital transfers for unplanned ICU management, extrapolating this as a parameter for secondary hospital safety after bariatric surgery.

METHODS

This was a retrospective, statewide, population-based, linked data cohort study capturing all adult bariatric surgery patients for an entire Australian state between 2007 and 2011 (n = 12,062) with minimum 12-month follow-up.

RESULTS

In secondary hospitals, 2663 (22.1%) bariatric patients were operated on, with the majority (n = 2553) undergoing sleeve gastrectomies (SG) or adjustable gastric bands (LAGB). Forty-two patients (including 19 LAGB and 20 SG) required inter-hospital transfer to a tertiary hospital for unplanned ICU care (1.6%, 95% confidence interval 1.2-2.1), mainly due to surgical complications. Inter-hospital transfers incurred two deaths, both following sleeve gastrectomies. When compared to patients requiring unplanned ICU admissions after bariatric surgery in tertiary hospitals with an on-site ICU (n = 155), there was no difference in their demographic parameters, comorbid illnesses, or mortality (4.8 vs 3.9%, p = 0.68). The mortality following bariatric procedures both statewide (0.2%) and in secondary hospitals (0.2%) was both uncommon and comparable.

CONCLUSIONS

Statewide inter-hospital transfers for unplanned ICU care from secondary hospitals were low. Inter-hospital transfer mortality was comparable to a similar bariatric cohort requiring unplanned ICU care after surgery in a tertiary hospital. This suggests that certain bariatric procedures can be safely done in most secondary hospitals where elective ICU admission is deemed unnecessary.

Acute kidney injury in bariatric surgery patients requiring intensive care admission: a state-wide, multicenter, cohort study

BACKGROUND

A multidisciplinary bariatric surgical approach is currently the most effective treatment for obesity. However, little is known about how the physiologic impact of weight reduction surgery superimposed on premorbid obesity-related co-morbidities may adversely influence perioperative renal function.

METHODS

This observational, multicenter study investigated all bariatric surgery patients (n = 590) admitted to any intensive care unit (ICU) in Western Australia between 2007 and 2011. Using Acute Kidney Injury Network (AKIN) criteria, we ascertained the incidence and contributing risk factors for acute kidney injury (AKI).

RESULTS

Acute kidney injury (AKI) occurred in 103 patients, accounting for 17.5% of all ICU admissions after bariatric surgery with 76.8% of the AKI episodes limited to AKIN stage 1. In a multivariate analysis, male gender, premorbid hypertension, higher admission APACHE II scores, and blood transfusions were all associated with AKI, while preexisting chronic kidney disease and body mass index (BMI) appeared not to influence renal decline. Both ICU (6.7 versus 2.5 d, P<.001) and hospital (18.6 versus 6.8 d, P<.001) length of stays were significantly increased after AKI. Six patients required hemodialysis while both ICU mortality (2.9 versus 0%, P = .005) and long-term mortality (18.2 versus 4.7 deaths per 1000 bariatric patient-yr, P = .01) were greater in patients experiencing AKI.

CONCLUSIONS

AKI is common in bariatric patients requiring critical care support leading to increased healthcare utilization, prolonged hospitalization, and is associated with a higher mortality. BMI, a previously described risk factor, was not predictive of AKI in this cohort.

A comparison of nonoliguric and oliguric severe acute kidney injury according to the risk injury failure loss end-stage (RIFLE) criteria

BACKGROUND

Risk, Injury, Failure, Loss, and End-Stage (RIFLE) criteria have been proposed as a standard definition of acute kidney injury (AKI). The most severe form of AKI, class F AKI, can be defined by either severe oliguria or a 3-fold increase in serum creatinine concentrations. We hypothesized that the outcomes of patients with these 2 alternative criteria of severe AKI were different.

METHODS

A prospective cohort study was conducted of all patients attaining RIFLE class F AKI during a 12-month period in a tertiary critical care facility.

RESULTS

Among a total of 2,379 critical care admissions, 129 (5.4%) fulfilled the serum creatinine criteria without oliguria (RIFLE class F) and 99 (4.2%) fulfilled oliguric (RIFLE class F) AKI criteria. Patients with oliguric AKI suffered a more severe disease process than nonoliguric AKI. Oliguric AKI was associated with a significantly higher risk of requiring acute dialysis (70.7 vs. 22.4%, p = 0.001), long-term dialysis >90 days (15 vs. 1.9%, p = 0.006), and hospital mortality (adjusted hazard ratio 3.33, 95% confidence interval, p = 0.001) than nonoliguric AKI.

CONCLUSIONS

Oliguric RIFLE class F AKI is a more severe form of AKI than nonoliguric class F AKI. These 2 forms of AKI should be considered separately when AKI is evaluated in a clinical trial.

Profound hypocalcaemia in a patient being anticoagulated with citrate for continuous renal replacement therapy

Citrate, as an anticoagulant for continuous renal replacement therapy in critically ill patients, has some potential advantages over heparin, including a prolonged dialysis filter life and reduced risk of bleeding. The key parameter involved in monitoring the adequacy and safety of citrate anticoagulation during continuous renal replacement therapy pertains to the ionised and total plasma calcium levels. We report a case of severe systemic hypocalcaemia during continuous renal replacement therapy with citrate anticoagulation resulting from relentless sequestration of calcium due to undiagnosed evolving rhabdomyolysis. Although excessive systemic citrate accumulation can also cause hypocalcaemia, this complication was not observed in our patient. While an acceptable lower limit of ionised calcium remains unknown, severe rhabdomyolysis needs to be considered when a patient's ionised calcium levels are not responsive to standard calcium replacement therapy during continuous renal replacement therapy using citrate anticoagulation in critically ill patients.

Meta-analysis of N-acetylcysteine to prevent acute renal failure after major surgery

BACKGROUND

Acute renal failure after major surgery is associated with significant mortality and morbidity that theoretically may be attenuated by N-acetylcysteine.

DESIGN

Meta-analysis of relevant studies sourced from the Cochrane Controlled Trial Register (2007 issue 4), EMBASE, and MEDLINE databases (1966 to February 1, 2008) without language restriction.

SETTING & POPULATION

Adult patients undergoing major surgery without the use of radiocontrast.

SELECTION CRITERIA FOR STUDIES

Randomized controlled studies comparing N-acetylcysteine with a placebo perioperatively.

DATA ANALYSIS

Categorical variables are reported as odds ratio (OR) with 95% confidence interval (CI), and continuous variables are reported as weighted-mean-difference (WMD) with 95% CI.

OUTCOME MEASURES

Effects of N-acetylcysteine on mortality and acute renal failure requiring dialysis were the main outcomes of interest. Additional outcome measures included an incremental increase in serum creatinine concentration greater than 25% above baseline, surgical reexploration for bleeding, amount of allogeneic blood transfusion, and length of intensive care unit stay.

RESULTS

10 studies involving a total of 1,193 adult patients undergoing major surgery were considered. N-Acetylcysteine use was not associated with a decrease in mortality (OR, 1.05; 95% CI, 0.58 to 1.92), acute renal failure requiring dialysis (OR, 1.04; 95% CI, 0.45 to 2.37), incremental increase in serum creatinine concentration greater than 25% above baseline (OR, 0.84; 95% CI, 0.64 to 1.11), or length of intensive care unit stay (WMD in days, 0.46; 95% CI, -0.43 to 1.36). N-acetylcysteine did not appear to increase the risk of surgical reexploration for bleeding (OR, 1.16; 95% CI, 0.57 to 2.38) or amount of allogeneic blood transfusion required (WMD in units, 0.31; 95% CI, -0.21 to 0.84).

LIMITATIONS

Most studied patients had cardiac surgery and normal renal function preoperatively.

CONCLUSIONS

There is no current evidence that N-acetylcysteine used perioperatively can alter mortality or renal outcomes when radiocontrast is not used.

Neuropsychological profile of young adults with spina bifida with or without hydrocephalus

OBJECTIVES

To determine the relative impact of hydrocephalus and spinal dysraphism in young adults on intellectual and cognitive functioning. Sub-groups of patients with congenital hydrocephalus and/or spina bifida were assessed between 1995 and 2003. The entry criteria were that individuals should have (i) intact global function, (ii) average verbal intelligence (or above), and (iii) should not have clinical depression. There were three sub-groups: patients with hydrocephalus and spina bifida, patients with hydrocephalus without spina bifida, and patients with spina bifida without hydrocephalus.

METHODS

Patients were neuropsychologically assessed as part of their normal clinical assessment during their annual medical review. Each individual completed a screening battery assessing global functioning, verbal intelligence, and mood. In addition they completed additional tests including measures of emotional intelligence, memory, attention, and executive function. Results were analysed to compare the performance of the patient sub-groups and to compare them to a healthy control group.

RESULTS

Patients with hydrocephalus (with or without spina bifida) were significantly impaired on the vast majority of all test scores as compared to patients with spina bifida and healthy controls. They were particularly poor on measures assessing executive function. By contrast for patients with spina bifida with no associated hydrocephalus, the significant majority of all test scores fell within the average range or above.

CONCLUSIONS

The neuropsychological profile of patients with hydrocephalus is one of relative impairment and this is so whether or not spina bifida is present. In spina bifida alone, in the absence of hydrocephalus, cognitive function is relatively spared.